Tinhorn

Originally an shortening of tinhorn gambler, a contemptuous term for a chuck-a-luck operator who is too poor (or cheap) to buy a proper leather dice-rolling horn. This was eventually expended from meaning 'cheap' to meaning 'cheap and flashy'.

Nowadays it means a person, particularly a gambler, who pretends to have more power, money, or information than he really does. It can also be used to mean a small-time operator.